Hollow shafts can be provided with sleeves, shells or other members along the exterior thereof and frequently lubrication of the outer surface of the hollow shaft may be desirable so that the outer member can move, e.g. axially along the hollow shaft. This can be the case, for example, in a clutch or coupling in which the outer member is keyed to the hollow shaft, is coupled therewith rotationally by a spline or other noncircular formation on the hollow shaft or is so connected to the hollow shaft that torque can be transmitted between them but relative axial movement is possible. The lubricant should be introduced between the juxtaposed surfaces of the hollow shaft and the surrounding member.
Lubricant-dispenser devices in the past have included lubricant containers, a piston displaceable in the lubricant container, an electrical circuit for driving the piston and some kind of manual switching arrangement which allows the circuit to be effective or ineffective with respect to the drive of the piston.
Usually these lubricating devices, especially if they include a gas-generating unit with, for example, an electrochemical gas-generating cell or a battery-driven electric motor system, have been located externally of the member to be lubricated and are either continuously operated whether or not the parts are rotating, or are operated by manual switching solely as a function of the turning on and off of a switch.
In cases in which a back and forth or oscillating or pendulum-type movement is superimposed upon an axial movement, lubrication of the outer surface of a machine part may not be possible with earlier devices and hence one may have to resort to manual lubrication at certain lubrication times during standstill of the apparatus.